1. Field of the Invention
The present invention relates generally to integrated circuits, and more particularly to a bidirectional switch circuitry for use in a floating circuit system.
2. Description of the Related Art
Recently, bidirectional switch circuits are becoming more widely used in the floating circuit systems as the speed and cost advantages of these systems increase. Typically, in the subscriber line-interface circuit (SLIC), a bidirectional switch integrated circuit is very important to switch bidirectionally the transmission paths of communication signals between a private branch exchange (PBX) and a terminal unit such as a telephone.
In the floating circuit system, it is known that a pair of unidirectional switch devices are combined to achieve a bidirectional switch function. The paired unidirectional switch devices are connected in parallel with each other to have the reverse current-forward directions. Generally, these switch devices are provided with two separate power supply units as the current drivers therefor, respectively. The power supply units are same as each other in the circuit configuration thereof.
The conventional bidirectional switch circuits suffer from the following problem: The employment of two power supply units causes the switch circuit to increase in the number of circuit components required, which are mounted at higher integration density on a semiconductor chip substrate of limited size. Obviously, this necessitates the use of a larger substrate, which results in the integrated circuit being increased in the manufacturing cost.